1. Field
Embodiments relate to a sensor and method for suppressing a background signal.
2. Description of the Related Art
In various sensing applications, due to a background signal, the accuracy of a signal to be detected may be reduced or the signal may not be detected. In particular, when the background signal is large, a sensor deviates from a dynamic range, which is a maximum range in which the sensor is able to perform detection and enters a saturation state. Therefore, a signal to be detected may not be distinguishable any more.
For example, in infrared imaging, a temperature differential to be detected is much smaller than the temperature of the background. As another example, in fluorescence imaging, light from an excitation source is directed toward to a target cell and light emitted by the cell itself is measured. In this case, the intensity of light emitted from the cell is much smaller than the excitation source. As another example, in a time-of-flight (TOF) type 3D image sensor that measures a travel time of light by radiating light on an object and detecting reflected and returned light, when background light has a high intensity, radiated and returned light and the background light both are incident on the sensor. Therefore, error may occur in depth, or each pixel of the image sensor enters a saturation state due to the background light, thereby not acquiring depth.
In various sensing applications, a sensor may include a temporal or spatial differential readout circuit in order to suppress the background signal of a common mode. The background signal may be suppressed by acquiring a differential signal by such a differential readout circuit. However, when the background signal has a high intensity or the background signal is accumulated for a long time because a sensing time is long, saturation occurs, thereby causing a desired signal not to be distinguishable from the background signal. Thus, there has been a research for a sensor employing a new structure and a method for preventing saturation due to a background signal.